‘Smash’ ends without bang

“Smash” (9 p.m.), NBC’s ambitious and highly promoted musical drama, wraps up tonight. It’s taken a whole season to build up the kind of soap-opera froth it should have generated in the early going.

Much of the problem with “Smash” is not just its deliberate pace, but that many of its “shocking” developments can be seen coming a mile away. Did anyone doubt that Uma Thurman’s character, Rebecca, would quit the show, leaving the mean, philandering director Derek (Jack Davenport) to choose between Karen (Katharine McPhee) and Ivy (Megan Hilty)? He makes his big choice tonight, just moments before curtain time. Try to act surprised.

• “American Masters” (8 p.m., PBS, check local listings) presents “Johnny Carson: King of Late Night.” This year marks the golden anniversary of Carson’s 1962 debut on “The Tonight Show” and 20 years since his retirement. “King” reminds us that Carson was present at the very birth of television, hosting one of the first hours of live TV on Omaha’s WOW network in 1949 and working for all three major networks throughout the 1950s.

Most of “King” is a wealth of clips spanning five decades and a parade of hosts and comics, including Jay Leno, David Letterman, Conan O’Brien, Arsenio Hall, Jimmy Fallon and Carson’s estranged permanent guest host, Joan Rivers. We also hear from comics such as Drew Carey, Jerry Seinfeld and Ray Romano, who describe success in the court of the king as the very threshold of stardom. And no discussion of Carson would be complete without a minor dissection of his peculiar relationship with sidekick Ed McMahon.